Correlation between TKI resistance and BM megakaryocyte numbers. Immunohistochemical staining for p16 (A) and p21 (B) in the BM biopsy specimens from four individual patients with CML are shown here. Images were obtained using a BX50 microscope using a ×20 objective lens. Scale bars, 20 μm. (C) Immunohistochemical staining for p16 and p21 in the healthy BM biopsy specimens. Representative results from 4 individual samples are shown. Images were obtained with a BZ-X700 microscope. Scale bars, 20 μm. (D) TKI-resistant index and megakaryocyte proportion in total BM cells in CML patients treated with imatinib or nilotinib. Pearson’s correlation coefficient was calculated and the actual R value is shown.